Some 30-second blocks of Super Bowl airtime are being sold for as high as $4 million — a $500,000 increase from the top seller in last year’s telecast, according to USA Today.

The research firm Kantar Media notes that the increase means that the price “is growing at three to five times the rate it did just a decade ago.”

“No one is holding a gun to the heads of these advertisers,” Jon Swallen, chief research officer at Kantar, told USA Today. “Clearly, these are price increases the market is willing to bear.” Swallen said he thinks the first 30-seconds-for-$5 million Super Bowl deal could air in 2016.

Those tuning in for the cola giants and other brand marketers suiting up for Game Day are in luck: The number of in-game ads has been going up, Swallen said.

One of the brands shelling out that kind of dough is M&M’s, which had a much-heralded spot in the last year’s Super Bowl. M&M’s won’t release its commercial or details of the ad in advance, according to a press release. However, the ad is tied to a new “Better With M” spot and socialcampaign that launched this week.[more]

M&M’s maker Mars has aired ads during the past three Super Bowls, with the first two focused on Snickers.

“Measured media spending on M&M’s grew from $87.7 million in 2010 to $103.7 million in 2011 and was at $97 million through October of last year,” Ad Age noted. “Snickers spending jumped from $64.8 million in 2010 to $85.6 million in 2011 and stood at $72.3 million through October.”

Among other brands readying their Super Bowl campaigns, Pepsi is gearing up for its half-time bonanza with Beyonce, while Coca-Cola is preparing a hybrid TV/digital campaign in a gamification move that will let viewers decide in real time how the storyline of Coca-Cola’s Big Game campaign will conclude.

Meanwhile, paper product manufacturer Dunder Mifflin — a brand made famous by NBC’s “The Office” — plans to run its first Super Bowl ad, and wants the public help it decide what the ad should be.

Crowdsourcing site Tongal.com is helping Dunder Mifflin — which is a business partnership between NBC Universal and Quill, a unit of Staples – sort out the public’s ideas, Mashable reports. The ad will only actually be seen during the game in the Scranton, Pa., area, where the fictional paper company is based, but will likely reach a broader audience via digital.

CBS’ own promotional efforts during the Super Bowl have yet to be fully revealed. Network CEO Les Moonves said last week that the network is aiming to have David Letterman appear during the broadcast, but wasn’t sure if it will happen, Ad Age reported.

Letterman or not, the network expects to promote “Under the Dome,” a 13-part series adapted from a Stephen King novel, scheduled to air on CBS in June.